arXiv subjects

Niharika Shrivastava

Publications and source records attributed to Niharika Shrivastava.

3 recordsLinked to original sources

arXiv2026

Twilight of the WIMP: Comprehensive Phenomenology of Electroweak Triplet Dark Matter

We present a comprehensive study of dark matter phenomenology in standard model extensions featuring an electroweak triplet scalar or fermion with hypercharge $Y = 0$ or $Y = 2$. These minimal triplet extensions provide well-motivated dark matter candidates stabilised by the $Z_2$ discrete symmetry. We perform a detailed analysis of the parameter space consistent with current cosmological and experimental constraints, including the relic abundance, direct detection limits, and indirect detection bounds. We find that the scalar triplet with $Y=0$ is ruled out by a combination of relic density, direct detection and indirect detection constraints. On the other hand, the scalar and fermionic triplets with $Y=2$ are both excluded by current direct detection experiments due to their large spin-independent scattering cross-sections. The viable parameter space of the remaining $Y=0$ fermion triplet dark matter lies within the projected sensitivity of near-future experiments, particularly those targeting indirect detection signatures. Collider prospects for these triplet extensions are also discussed in the Appendix.

hep-ph↗

arXiv2025

MS-GAGA: Metric-Selective Guided Adversarial Generation Attack

We present MS-GAGA (Metric-Selective Guided Adversarial Generation Attack), a two-stage framework for crafting transferable and visually imperceptible adversarial examples against deepfake detectors in black-box settings. In Stage 1, a dual-stream attack module generates adversarial candidates: MNTD-PGD applies enhanced gradient calculations optimized for small perturbation budgets, while SG-PGD focuses perturbations on visually salient regions. This complementary design expands the adversarial search space and improves transferability across unseen models. In Stage 2, a metric-aware selection module evaluates candidates based on both their success against black-box models and their structural similarity (SSIM) to the original image. By jointly optimizing transferability and imperceptibility, MS-GAGA achieves up to 27% higher misclassification rates on unseen detectors compared to state-of-the-art attacks.

cs.CV↗

arXiv2024

Search for MeV Gamma-ray emission from TeV bright red dwarfs with COMPTEL

The SHALON atmospheric Cherenkov telescope has detected very high energy gamma-ray emission at TeV energies from eight red dwarfs, namely, V388 Cas, V547 Cas, V780 Tau, V962 Tau, V1589 Cyg, GJ 1078, GJ 3684 and GL 851.1. Consequently, these red dwarfs have been suggested as sources of ultra-high energy cosmic rays. In this work, we search for soft gamma-ray emission from these TeV bright red dwarfs between 0.75-30 MeV using archival data from the COMPTEL gamma-ray imaging telescope, as a follow-up to a similar search for GeV gamma-ray emission using the Fermi-LAT telescope. Although, prima-facie, we detect non-zero photon flux from three red dwarfs with high significance, these signals can attributed to contamination from nearby sources such as Crab and Cygnus, which are within the angular resolution of COMPTEL, and have been previously detected as very bright point sources at MeV energies. Therefore, we could not detect any statistically significant signal ($>3σ$) from any of these eight red dwarfs from 0.75-30 MeV. We then report the 95% confidence level upper limits on the differential photon flux (at 30 MeV), integral photon flux and integral energy flux for all of the eight red dwarfs. The integral energy flux limits range between $10^{-11}-10^{-10} \rm{ergs/cm^2/s}$.

astro-ph.HE↗